The class of thermoplastic polymers is well known in the art, in part because of the useful characteristic of many of such materials of being heat deformable at relatively low temperatures. Such thermoplastics are processed by conventional methods such as extrusion, injection molding or thermoforming into films, sheets, fibers and molded objects of established utility. The physical performance of many if not most thermoplastics suffers, however, when the plastic encounters elevated temperatures or when the plastic is exposed to light, particularly ultra violet light, over an extended period of time. Most thermoplastics undergo some degree of degradation, and in some cases substantial degradation, when maintained under the influence of heat and/or light. As a result, it is frequently if not customarily advantageous to provide protection against the detrimental effects of heat and/or light by incorporating within the thermoplastic one or more stabilizers. Such heat or light stabilizers are particularly necessary in the case of engineering thermoplastics where exposure to elevated temperatures is anticipated either because of the relatively high processing temperatures required or because of a forseen application of the thermoplastic at high temperature.
Many of the conventional stabilizers contain atoms other than carbon and hydrogen and a number of the stabilizers contain heterocyclic rings. Russell et al, U.S. Pat. No. 3,929,729 and U.S. Pat. No. 4,024,104, disclose the use of certain benzophenones and certain benzotriazoles as heat stabilizers in olefin-carbon monoxide polymers. Mercaptobenzothiazoles are a well known class of such stabilizers. It would be of advantage to provide a novel class of heterocyclic heat or light stabilizers for thermoplastic polymers.